The Effects of Paclobutrazol on the Growth and Movement of 14c Labelled Assimilates in Red Delicious Apple Seedlings

El-Hodairi, M. H.; Canham, A. E.

doi:10.17660/actahortic.1990.279.40

Cited by 5 publications

(4 citation statements)

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“…In a study examining PGR effects on turfgrass photoassimilate partitioning, several PGR increased photoassimilate partitioning to adjacent tillers (Hanson and Branham, 1987). In other agronomic crops similar changes in photoassimlate distribution in PGR‐treated plants have been observed (Huang et al, 1995; El‐Hodairi et al, 1988).…”

Section: Discussionsupporting

confidence: 69%

Plant Growth Regulators Alter Kentucky Bluegrass Canopy Leaf Area and Carbon Exchange

2007

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Turf managers apply plant growth regulators (PGRs) throughout the growing season to reduce clipping production, provide a uniform canopy, and increase color. Reduced efficacy of trinexapac‐ethyl (TE) [4‐(cyclopropyl‐α‐hydroxy‐methylene)‐3,5‐dioxocyclohexanecarboxylic acid ethyl ester] and paclobutrazol (PAC) [(2RS, 3RS)‐1‐(4‐chlorophenyl)‐4,4‐dimethyl‐2‐(1H‐1,2,4‐triazol‐1‐yl) pentan‐3‐ol] has been reported during warmer summer months. Plant growth regulator dissipation and Kentucky bluegrass (KBG; Poa pratensis L.) clipping production, canopy leaf area, and carbon exchange rates (CERs) were measured following single TE or PAC applications applied at three rates and three application timings. Warmer summer conditions reduced the intensity and duration of TE and PAC growth suppression compared to spring applications. Plant growth regulator applications above the manufacturers label rate provided no additional suppression. Residues of PGRs were analyzed by HPLC‐UV. Warmer temperatures increased TE and PAC uptake, but accelerated the rate of PGR dissipation. Carbon exchange rates were measured weekly on ground (CERG) and leaf (CERL) area bases. Treatment with PGRs resulted in decreased leaf area early during inhibition followed by increased rate of leaf area production. Changes in canopy leaf area were greatest in spring and PAC caused the greatest change in leaf area. Changes in CERG reflected changes in leaf area. Paclobutrazol generally increased CERL during periods of clipping suppression, while TE had no effect on CERL.

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Section: Discussionsupporting

confidence: 69%

Plant Growth Regulators Alter Kentucky Bluegrass Canopy Leaf Area and Carbon Exchange

2007

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“…Because no link in CERs and changes in plant growth are evident, altered photoassimilate partitioning seems a more plausible explanation. Changes in photoassimilate partitioning from PGR application have been previously reported on other species (Huang et al, 1995; El‐Hodairi et al, 1988). Hanson and Branham (1987) reported PAC to shift photoassimilates into adjacent tillers weeks after treatment.…”

Section: Discussionsupporting

confidence: 65%

Trinexapac‐ethyl and Paclobutrazol Affect Kentucky Bluegrass Single‐Leaf Carbon Exchange Rates and Plant Growth

Beasley

Branham

2007

Crop Science

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Trinexapac‐ethyl (TE) [4‐(cyclopropyl‐α‐hydroxy‐methylene)‐3,5‐dioxocyclohexanecarboxylic acid ethyl ester] and paclobutrazol (PAC) [(2RS,3RS)‐1‐(4‐chlorophenyl)‐4,4‐dimethyl‐2‐(1H‐1,2,4‐triazol‐1‐yl)pentan‐3‐ol] are routinely used to suppress clipping production. Single‐leaf turfgrass C exchange rates (CERs) in response to plant growth regulator (PGR) treatment have not been characterized. Individual Kentucky bluegrass (KBG, Poa pratensis L.) plants received label rates of TE or PAC and were placed in growth chambers at 23/18 or 30/25°C. Photosynthetic efficiency and CER measurements were recorded every 4 d for 44 d. Total root length (TRL), root surface area (SA), and average root diameter were measured at the end of the study. Reductions in CERs of TE‐ or PAC‐treated plants were short lived with CERs suppressed 17 to 29% of control (POC) at 4 and 12 days after treatment (DAT), respectively. Plants treated at 23/18°C with PGRs typically had short‐lived increases in CERs following CER suppression. A similar pattern of CER response to PGR treatment was observed at the 30/25°C temperature regime. Quantum efficiency was unaffected, but plants treated with PGRs had reduced root growth. PAC caused the greatest reduction in TRL and SA while increasing root diameter. A decline in TRL and SA in conjunction with increased tillering indicates that PGR reduced TRL and SA on a tiller basis. Changes in single‐leaf CERs do not fully explain PGR‐induced changes in plant growth.

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“…Differences in root architecture and tillering between TE-treated and control plants may be the result of altered carbon exchange rates (CERs) and/or photoassimilate partitioning. Other agronomic commodities treated with PGRs have shown decreased and/or increased CERs as well as altered photoassimilate partitioning (El-Hodairi et al, 1988;Huang et al, Fig. 4.…”

Section: Resultsmentioning

confidence: 99%

Trinexapac-ethyl Affects Kentucky Bluegrass Root Architecture

Beasley¹,

Branham²,

Ortiz-Ribbing³

2005

HortSci

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Trinexapac-ethyl (TE) [4-(cyclopropyl-a-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] effects on turfgrass root architecture are not known. It has been postulated that PGR application could cause photoassimilate that is normally used for shoot growth to be funneled to root growth. This study evaluated the effects of a single TE application on kentucky bluegrass (KBG) root and shoot growth for seven weeks. Individual KBG plants were grown in a hydroponic system and harvested weekly. At each harvest, tiller height, tiller number, and color ratings were recorded. Estimates of total root length (TRL), root surface area (SA), and average root diameter were measured using the WinRhizo system. Trinexapac-ethyl reduced plant height for 4 weeks followed by a period of postinhibition growth enhancement. Trinexapac-ethyl increased tiller number over the course of the study and slightly enhanced plant color. Trinexapac-ethyl reduced TRL and SA 48% and 46% at 1 week after treatment (WAT) followed by an accelerated growth rate 1 to 4 WAT. Trinexapac-ethyl had no effect on root diameter. On a tiller basis, TE initially reduced TRL and SA 30% and 31%, respectively. Total root length per tiller and root surface area per tiller were reduced by TE treatment, but by 7 WAT, those differences were no longer significant. Initial reductions in TRL and SA per tiller may reduce tiller competitiveness for water and nutrients. Based on data for TRL and SA per tiller, shoot and root growth must be considered in total to fully understand TE effects on plant growth. Field research is needed to corroborate results from hydroponic-studies and examine the effect of various TE rates and multiple applications on turfgrass root and shoot growth.

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The Effects of Paclobutrazol on the Growth and Movement of 14c Labelled Assimilates in Red Delicious Apple Seedlings

Cited by 5 publications

References 0 publications

Plant Growth Regulators Alter Kentucky Bluegrass Canopy Leaf Area and Carbon Exchange

Plant Growth Regulators Alter Kentucky Bluegrass Canopy Leaf Area and Carbon Exchange

Trinexapac‐ethyl and Paclobutrazol Affect Kentucky Bluegrass Single‐Leaf Carbon Exchange Rates and Plant Growth

Trinexapac-ethyl Affects Kentucky Bluegrass Root Architecture

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